An ordered list, created using the OL
element, should contain information where order should be emphasized,
as in a recipe:

Mix dry ingredients thoroughly.

Pour in wet ingredients.

Mix for 10 minutes.

Bake for one hour at 300 degrees.

Definition lists, created using the DL
element, generally consist of a series of term/definition pairs
(although definition lists may have other applications). Thus, when
advertising a product, one might use a definition list:

Lower cost

The new version of this product costs significantly less than the
previous one!

Easier to use

We've changed the product so that it's much easier to use!

Safe for kids

You can leave your kids alone in a room with this product and
they won't get hurt (not a guarantee).

defined in HTML as:

<DL>
<DT><STRONG>Lower cost</STRONG>
<DD>The new version of this product costs significantly less than the
previous one!
<DT><STRONG>Easier to use</STRONG>
<DD>We've changed the product so that it's much easier to use!
<DT><STRONG>Safe for kids</STRONG>
<DD>You can leave your kids alone in a room with this product and
they won't get hurt (not a guarantee).
</DL>

Lists may also be nested and different list types may be used
together, as in the following example, which is a definition list that
contains an unordered list (the ingredients) and an
ordered list (the procedure):

The ingredients:

100 g. flour

10 g. sugar

1 cup water

2 eggs

salt, pepper

The procedure:

Mix dry ingredients thoroughly.

Pour in wet ingredients.

Mix for 10 minutes.

Bake for one hour at 300 degrees.

Notes:

The recipe may be improved by adding raisins.

The exact presentation of the three list types depends on the user
agent. We discourage authors from using lists purely as a means of
indenting text. This is a stylistic issue and is properly handled by
style sheets.

Deprecated.
For OL only. This attribute specifies
the starting number of the first item in an ordered list. The default
starting number is "1". Note that while the value of this attribute is
an integer, the corresponding label may be non-numeric.
Thus, when the list item style is upper case latin letters (A, B, C, ...),
start=3 means "C". When the style is lower case roman numerals,
start=3 means "iii", etc.

Deprecated.
For LI only. This attribute sets the
number of the current list item. Note that while the value of this
attribute is an integer, the corresponding label may be non-numeric
(see the <start> attribute).

Ordered and unordered lists are rendered in an identical manner
except that visual user agents number ordered list items. User agents
may present those numbers in a variety of ways. Unordered list items
are not numbered.

Both types of lists are made up of sequences of list items defined
by the LI element
(whose end tag may be omitted).

Details about number order. In ordered lists, it
is not possible to continue list numbering automatically from a
previous list or to hide numbering of some list items. However, authors
can reset the number of a list item by setting its value attribute. Numbering continues from the new
value for subsequent list items. For example:

Definition lists vary only slightly from other types of lists in
that list items consist of two parts: a term and a description. The
term is given by the DT element and is
restricted to inline content. The description is given with a DD element that contains block-level
content.

Here is an example:

<DL>
<DT>Dweeb
<DD>young excitable person who may mature
into a <EM>Nerd</EM> or <EM>Geek</EM>
<DT>Cracker
<DD>hacker on the Internet
<DT>Nerd
<DD>male so into the Net that he forgets
his wife's birthday
</DL>

Here is an example with multiple terms and descriptions:

<DL>
<DT>Center
<DT>Centre
<DD> A point equidistant from all points
on the surface of a sphere.
<DD> In some field sports, the player who
holds the middle position on the field, court,
or forward line.
</DL>

Another application of DL, for example, is
for marking up dialogues, with each DT
naming a speaker, and each DD containing
his or her words.

Note.The following is an
informative description of the behavior of some current visual user
agents when formatting lists. Style sheets allow better control of
list formatting (e.g., for numbering, language-dependent conventions,
indenting, etc.).

Visual browsers usually present nested lists indented with respect
to the current level of indentation.

For both OL and UL, the type
attribute specifies rendering options for visual user agents.

For the UL element, possible values for
the type attribute are
disc, square, and
circle. The default value depends on the level of
nesting of the current list. These values are case-insensitive.

How each value is presented depends on the user agent. User agents
should attempt to present a "disc" as a small filled-in circle,
a "circle" as a small circle outline, and a "square" as a
small square outline.

Your user agent displays them as follows (the bullet glyph in the
line may or may not vary):

is produced by the value "disc"

is produced by the value "square"

is produced by the value "circle"

For the OL element, possible values for
the type attribute are summarized
in the table below (the are case-sensitive):

Type

Numbering style

1

arabic numbers

1, 2, 3, ...

a

lower alpha

a, b, c, ...

A

upper alpha

A, B, C, ...

i

lower roman

i, ii, iii, ...

I

upper roman

I, II, III, ...

Note that the type attribute is deprecated and list styles
should be handled through style sheets.

For
example, using CSS, one may specify that the style of numbers for list
elements in a numbered list should be lower case roman numerals. In
the excerpt below, every OL element
belonging to the class "withroman" will have roman numerals in front
of its list items.

The rendering of a definition list also depends on the user
agent. Your user agent renders this example:

<DL>
<DT>Dweeb
<DD>young excitable person who may mature
into a <EM>Nerd</EM> or <EM>Geek</EM>
<DT>Cracker
<DD>hacker on the Internet
<DT>Nerd
<DD>male so into the Net that he forgets
his wife's birthday
</DL>

The DIR element was designed to be used for
creating multicolumn directory lists. The MENU
element was designed to be used for single column menu lists. Both elements
have the same structure as UL, just different
rendering. In practice, a user agent will render a DIR or MENU list exactly as
a UL list.